Some mission-critical servers and storage systems employ Redundant Array of Inexpensive Drives (RAID) disk controllers for fault tolerance to reduce the likelihood of data loss in the event of a hardware fault. To improve performance, many RAID controllers use a RAID cache. A RAID cache provides temporary storage for data transfers between host and disk subsystems. Typically, such RAID cache is implemented with a dynamic random access memory (DRAM) based dual in-line memory modules (DIMM) (e.g., 256 MB-4 GB capacity). RAID cache data loss can occur in the event of a power failure. The cache often will momentarily contain the only copy of a piece of write data until that data can be written to the disk If power is lost before data is written to the disk, the data is gone forever. To avoid data loss on power fail, some prior art RAID cache DIMM's are backed-up by batteries. When the system power fails, the battery kicks in to supply power to the DIMM, thus sustaining the data until power can be restored. Once power is restored, the “dirty” data in the cache is flushed to disk.
However, such use of batteries to provide backup power to the RAID cache DIMM's means that the batteries may need to be replaced regularly which is inconvenient and hinders the availability of the RAID DIMM. Consequently, a way is needed to provide backup to the cache and/or memory DIMM's that does not rely on batteries.